On intra mode propagation

ABSTRACT

Coded information of (i) a current block of a picture and (ii) a reconstructed area of the picture is received. A matching area of the current block in the reconstructed area of the picture is determined. A first corresponding position of the current block is determined inside the current block. The first corresponding position includes a first coordinate value on a first axis and a second coordinate value on a second axis relative to a first reference point on the current block. A corresponding block of the current block is determined in the matching area. The corresponding block includes a second corresponding position that has the first coordinate value on the first axis and the second coordinate value on the second axis relative to a second reference point on the matching area. An intra prediction mode of the current block is determined based on the corresponding block.

INCORPORATION BY REFERENCE

This present disclosure claims the benefit of priority to U.S.Provisional Application No. 63/254,526, “Intra Mode Propagation” filedon Oct. 11, 2021, which is incorporated by reference herein in itsentirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding can be performed using inter-pictureprediction with motion compensation. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has specific bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GBytes of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce the aforementioned bandwidth and/or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless compression and lossy compression, as well as a combinationthereof can be employed. Lossless compression refers to techniques wherean exact copy of the original signal can be reconstructed from thecompressed original signal. When using lossy compression, thereconstructed signal may not be identical to the original signal, butthe distortion between original and reconstructed signals is smallenough to make the reconstructed signal useful for the intendedapplication. In the case of video, lossy compression is widely employed.The amount of distortion tolerated depends on the application; forexample, users of certain consumer streaming applications may toleratehigher distortion than users of television distribution applications.The compression ratio achievable can reflect that: higherallowable/tolerable distortion can yield higher compression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding.

Video codec technologies can include techniques known as intra coding.In intra coding, sample values are represented without reference tosamples or other data from previously reconstructed reference pictures.In some video codecs, the picture is spatially subdivided into blocks ofsamples. When all blocks of samples are coded in intra mode, thatpicture can be an intra picture. Intra pictures and their derivationssuch as independent decoder refresh pictures, can be used to reset thedecoder state and can, therefore, be used as the first picture in acoded video bitstream and a video session, or as a still image. Thesamples of an intra block can be exposed to a transform, and thetransform coefficients can be quantized before entropy coding. Intraprediction can be a technique that minimizes sample values in thepre-transform domain. In some cases, the smaller the DC value after atransform is, and the smaller the AC coefficients are, the fewer thebits that are required at a given quantization step size to representthe block after entropy coding.

Traditional intra coding such as known from, for example MPEG-2generation coding technologies, does not use intra prediction. However,some newer video compression technologies include techniques thatattempt, from, for example, surrounding sample data and/or metadataobtained during the encoding and/or decoding of spatially neighboring,and preceding in decoding order, blocks of data. Such techniques arehenceforth called “intra prediction” techniques. Note that in at leastsome cases, intra prediction is using reference data only from thecurrent picture under reconstruction and not from reference pictures.

There can be many different forms of intra prediction. When more thanone of such techniques can be used in a given video coding technology,the technique in use can be coded in an intra prediction mode. Incertain cases, modes can have submodes and/or parameters, and those canbe coded individually or included in the mode codeword. Which codewordto use for a given mode, submode, and/or parameter combination can havean impact in the coding efficiency gain through intra prediction, and socan the entropy coding technology used to translate the codewords into abitstream.

A certain mode of intra prediction was introduced with H.264, refined inH.265, and further refined in newer coding technologies such as jointexploration model (JEM), versatile video coding (VVC), and benchmark set(BMS). A predictor block can be formed using neighboring sample valuesbelonging to already available samples. Sample values of neighboringsamples are copied into the predictor block according to a direction. Areference to the direction in use can be coded in the bitstream or mayitself be predicted.

Referring to FIG. 1 , depicted in the lower right is a subset of ninepredictor directions known from H.265's 33 possible predictor directions(corresponding to the 33 angular modes of the 35 intra modes). The pointwhere the arrows converge (101) represents the sample being predicted.The arrows represent the direction from which the sample is beingpredicted. For example, arrow (102) indicates that sample (101) ispredicted from a sample or samples to the upper right, at a 45 degreeangle from the horizontal. Similarly, arrow (103) indicates that sample(101) is predicted from a sample or samples to the lower left of sample(101), in a 22.5 degree angle from the horizontal.

Still referring to FIG. 1 , on the top left there is depicted a squareblock (104) of 4×4 samples (indicated by a dashed, boldface line). Thesquare block (104) includes 16 samples, each labelled with an “S”, itsposition in the Y dimension (e.g., row index) and its position in the Xdimension (e.g., column index). For example, sample S21 is the secondsample in the Y dimension (from the top) and the first (from the left)sample in the X dimension. Similarly, sample S44 is the fourth sample inblock (104) in both the Y and X dimensions. As the block is 4×4 samplesin size, S44 is at the bottom right. Further shown are reference samplesthat follow a similar numbering scheme. A reference sample is labelledwith an R, its Y position (e.g., row index) and X position (columnindex) relative to block (104). In both H.264 and H.265, predictionsamples neighbor the block under reconstruction; therefore no negativevalues need to be used.

Intra picture prediction can work by copying reference sample valuesfrom the neighboring samples as appropriated by the signaled predictiondirection. For example, assume the coded video bitstream includessignaling that, for this block, indicates a prediction directionconsistent with arrow (102)—that is, samples are predicted from aprediction sample or samples to the upper right, at a 45 degree anglefrom the horizontal. In that case, samples S41, S32, S23, and S14 arepredicted from the same reference sample R05. Sample S44 is thenpredicted from reference sample R08.

In certain cases, the values of multiple reference samples may becombined, for example through interpolation, in order to calculate areference sample; especially when the directions are not evenlydivisible by 45 degrees.

The number of possible directions has increased as video codingtechnology has developed. In H.264 (year 2003), nine different directioncould be represented. That increased to 33 in H.265 (year 2013), andJEM/VVC/BMS, at the time of disclosure, can support up to 65 directions.Experiments have been conducted to identify the most likely directions,and certain techniques in the entropy coding are used to represent thoselikely directions in a small number of bits, accepting a certain penaltyfor less likely directions. Further, the directions themselves cansometimes be predicted from neighboring directions used in neighboring,already decoded, blocks.

FIG. 2 shows a schematic (201) that depicts 65 intra predictiondirections according to JEM to illustrate the increasing number ofprediction directions over time.

The mapping of intra prediction directions bits in the coded videobitstream that represent the direction can be different from videocoding technology to video coding technology; and can range, forexample, from simple direct mappings of prediction direction to intraprediction mode, to codewords, to complex adaptive schemes involvingmost probable modes, and similar techniques. In all cases, however,there can be certain directions that are statistically less likely tooccur in video content than certain other directions. As the goal ofvideo compression is the reduction of redundancy, those less likelydirections will, in a well working video coding technology, berepresented by a larger number of bits than more likely directions.

SUMMARY

Aspects of the disclosure provide methods and apparatuses for videoencoding/decoding. In some examples, an apparatus for video decodingincludes receiving circuitry and processing circuitry.

According to an aspect of the disclosure, a method of video decodingperformed in a video decoder is provided. In the method, codedinformation of (i) a current block of a picture and (ii) a reconstructedarea of the picture can be received from a coded video bitstream. Amatching area of the current block in the reconstructed area of thepicture can be determined. A first corresponding position of the currentblock can be determined inside the current block. The firstcorresponding position can include a first coordinate value on a firstaxis and a second coordinate value on a second axis relative to a firstreference point on the current block. The first axis can beperpendicular to the second axis. A corresponding block of the currentblock can be determined in the matching area. The corresponding blockcan include a second corresponding position that has the firstcoordinate value on the first axis and the second coordinate value onthe second axis relative to a second reference point on the matchingarea. An intra prediction mode of the current block can be determinedbased on the corresponding block.

To determine the matching area, a plurality of candidate matching areascan be searched in the reconstructed area of the picture. A respectivecost value between a template region of the current block and arespective template region of each of the plurality candidate matchingareas can be determined. The matching area can be determined as acandidate matching area with a minimum cost value from the plurality ofcandidate matching areas. The template region of the current block caninclude a first region adjacent to a left side of the current block anda second region adjacent to a top side of the current block. Therespective template region of each of the plurality of candidatematching areas can include a first region adjacent to a left side of therespective one of the plurality of candidate matching areas and a secondregion adjacent to a top side of the respective one of the plurality ofcandidate matching areas.

In some embodiments, the first corresponding position of the currentblock can be predefined or signaled in the coded information.

In some embodiments, the first corresponding position can be the centerof the current block.

In some embodiments, an intra prediction mode of the corresponding blockcan be determined as the intra prediction mode of the current block.

In some embodiments, the intra prediction mode of the current block canbe determined based on a universal intra mode map. The universal intramode map can divide the matching area into a plurality of sub areas.Each of the plurality of sub areas can be associated with a respectiveintra prediction mode. The intra prediction mode of the current blockcan be the intra prediction mode associated with a sub area of theplurality of sub areas that includes the second corresponding position.

According to another aspect of the disclosure, a method of video codingperformed in a video decoder can be provided. In the method, (i) achroma coding unit (CU) and (ii) a luma area can be received from acoded video bitstream. A corresponding position of the chroma CU can bedetermined inside the chroma CU. The corresponding position can includea first coordinate value on a first axis and a second coordinate valueon a second axis. The first axis can be perpendicular to the secondaxis. A collocated luma CU of the chroma CU can be determined in theluma area. The collocated luma CU can include the correspondingposition. An intra prediction mode of the chroma CU can be determinedbased on the collocated luma CU.

In an embodiment, in response to the collocated luma CU being intracoded based on an intra prediction mode, the intra prediction mode ofthe collocated luma CU can be determined as the intra prediction mode ofthe chroma CU. In other embodiments, in response to the collocated lumaCU not being intra coded, a propagated intra mode of the collocated lumaCU can be determined as the intra prediction mode of the chroma CU. Thepropagated intra mode of the collocated luma CU can be obtained based onintra prediction modes of neighboring luma CUs of the collocated lumaCU.

In some embodiments, the corresponding position of the chroma CU can bepredefined or signaled in the coded information.

In some embodiments, the intra prediction mode of the chroma CU can bedetermined based on a universal intra mode map. The universal intra modemap can divide the luma area into a plurality of sub areas. Each of theplurality of sub areas can be assigned with a respective intraprediction mode. The intra prediction mode of the chroma CU can be theintra prediction mode associated with a sub area of the plurality of subareas that includes the corresponding position.

According to another aspect of the disclosure, an apparatus is provided.The apparatus includes processing circuitry. The processing circuitrycan be configured to perform any of the methods for video coding.

Aspects of the disclosure also provide a non-transitorycomputer-readable medium storing instructions which when executed by acomputer for video coding cause the computer to perform any of themethods for video coding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of an exemplary subset of intraprediction modes.

FIG. 2 is an illustration of exemplary intra prediction directions.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system (300) in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of acommunication system (400) in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 6 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 7 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 8 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 9 shows neighboring coding units of a current coding unit in intramode coding according to some embodiments of the disclosure.

FIG. 10 is a schematic illustration of an intra template matchingprediction (TMP) according to some embodiments of the disclosure.

FIG. 11 is a schematic illustration of a derived mode (DM) for chromaaccording to some embodiments of the disclosure.

FIG. 12A is a first exemplary universal intra mode map according to someembodiments of the disclosure.

FIG. 12B is a second exemplary universal intra mode map according tosome embodiments of the disclosure.

FIG. 13 is a schematic illustration of a first exemplary propagatedintra mode based on TMP according to some embodiments of the disclosure.

FIG. 14 is a schematic illustration of a second exemplary propagatedintra mode based on TMP according to some embodiments of the disclosure.

FIG. 15 shows a flow chart outlining a first exemplary decoding processaccording to some embodiments of the disclosure.

FIG. 16 shows a flow chart outlining a second exemplary decoding processaccording to some embodiments of the disclosure.

FIG. 17 shows a flow chart outlining a first exemplary encoding processaccording to some embodiments of the disclosure.

FIG. 18 shows a flow chart outlining a second exemplary encoding processaccording to some embodiments of the disclosure.

FIG. 19 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 3 illustrates a simplified block diagram of a communication system(300) according to an embodiment of the present disclosure. Thecommunication system (300) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (350). Forexample, the communication system (300) includes a first pair ofterminal devices (310) and (320) interconnected via the network (350).In the FIG. 3 example, the first pair of terminal devices (310) and(320) performs unidirectional transmission of data. For example, theterminal device (310) may code video data (e.g., a stream of videopictures that are captured by the terminal device (310)) fortransmission to the other terminal device (320) via the network (350).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (320) may receive the codedvideo data from the network (350), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (300) includes a secondpair of terminal devices (330) and (340) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (330) and (340)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (330) and (340) via the network (350). Eachterminal device of the terminal devices (330) and (340) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (330) and (340), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 3 example, the terminal devices (310), (320), (330) and(340) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (350) represents any number ofnetworks that convey coded video data among the terminal devices (310),(320), (330) and (340), including for example wireline (wired) and/orwireless communication networks. The communication network (350) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(350) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 4 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (413), that caninclude a video source (401), for example a digital camera, creating forexample a stream of video pictures (402) that are uncompressed. In anexample, the stream of video pictures (402) includes samples that aretaken by the digital camera. The stream of video pictures (402),depicted as a bold line to emphasize a high data volume when compared toencoded video data (404) (or coded video bitstreams), can be processedby an electronic device (420) that includes a video encoder (403)coupled to the video source (401). The video encoder (403) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (404) (or encoded video bitstream (404)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (402), can be stored on a streamingserver (405) for future use. One or more streaming client subsystems,such as client subsystems (406) and (408) in FIG. 4 can access thestreaming server (405) to retrieve copies (407) and (409) of the encodedvideo data (404). A client subsystem (406) can include a video decoder(410), for example, in an electronic device (430). The video decoder(410) decodes the incoming copy (407) of the encoded video data andcreates an outgoing stream of video pictures (411) that can be renderedon a display (412) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (404),(407), and (409) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (420) and (430) can includeother components (not shown). For example, the electronic device (420)can include a video decoder (not shown) and the electronic device (430)can include a video encoder (not shown) as well.

FIG. 5 shows a block diagram of a video decoder (510) according to anembodiment of the present disclosure. The video decoder (510) can beincluded in an electronic device (530). The electronic device (530) caninclude a receiver (531) (e.g., receiving circuitry). The video decoder(510) can be used in the place of the video decoder (410) in the FIG. 4example.

The receiver (531) may receive one or more coded video sequences to bedecoded by the video decoder (510); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (501), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (531) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (531) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (515) may be coupled inbetween the receiver (531) and an entropy decoder/parser (520) (“parser(520)” henceforth). In certain applications, the buffer memory (515) ispart of the video decoder (510). In others, it can be outside of thevideo decoder (510) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (510), forexample to combat network jitter, and in addition another buffer memory(515) inside the video decoder (510), for example to handle playouttiming. When the receiver (531) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (515) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (515) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (510).

The video decoder (510) may include the parser (520) to reconstructsymbols (521) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (510),and potentially information to control a rendering device such as arender device (512) (e.g., a display screen) that is not an integralpart of the electronic device (530) but can be coupled to the electronicdevice (530), as was shown in FIG. 5 . The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (520) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (520) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (520) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (520) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (515), so as tocreate symbols (521).

Reconstruction of the symbols (521) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (520). The flow of such subgroup control information between theparser (520) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (510)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (551). Thescaler/inverse transform unit (551) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (521) from the parser (520). The scaler/inversetransform unit (551) can output blocks comprising sample values, thatcan be input into aggregator (555).

In some cases, the output samples of the scaler/inverse transform (551)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (552). In some cases, the intra pictureprediction unit (552) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (558). The currentpicture buffer (558) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(555), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (552) has generated to the outputsample information as provided by the scaler/inverse transform unit(551).

In other cases, the output samples of the scaler/inverse transform unit(551) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (553) canaccess reference picture memory (557) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (521) pertaining to the block, these samples can beadded by the aggregator (555) to the output of the scaler/inversetransform unit (551) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (557) from where themotion compensation prediction unit (553) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (553) in the form of symbols (521) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (557) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (555) can be subject to variousloop filtering techniques in the loop filter unit (556). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (556) as symbols (521) from the parser (520), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (556) can be a sample stream that canbe output to the render device (512) as well as stored in the referencepicture memory (557) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (520)), the current picture buffer (558) can becomea part of the reference picture memory (557), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (510) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (510) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 6 shows a block diagram of a video encoder (603) according to anembodiment of the present disclosure. The video encoder (603) isincluded in an electronic device (620). The electronic device (620)includes a transmitter (640) (e.g., transmitting circuitry). The videoencoder (603) can be used in the place of the video encoder (403) in theFIG. 4 example.

The video encoder (603) may receive video samples from a video source(601) (that is not part of the electronic device (620) in the FIG. 6example) that may capture video image(s) to be coded by the videoencoder (603). In another example, the video source (601) is a part ofthe electronic device (620).

The video source (601) may provide the source video sequence to be codedby the video encoder (603) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (601) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (601) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (603) may code andcompress the pictures of the source video sequence into a coded videosequence (643) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (650). In some embodiments, the controller(650) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (650) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (650) can be configured to have other suitablefunctions that pertain to the video encoder (603) optimized for acertain system design.

In some embodiments, the video encoder (603) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (630) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (633)embedded in the video encoder (603). The decoder (633) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (634). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (634) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (633) can be the same as of a“remote” decoder, such as the video decoder (510), which has alreadybeen described in detail above in conjunction with FIG. 5 . Brieflyreferring also to FIG. 5 , however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (645) and the parser (520) can be lossless, the entropy decodingparts of the video decoder (510), including the buffer memory (515), andparser (520) may not be fully implemented in the local decoder (633).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (630) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously coded picture fromthe video sequence that were designated as “reference pictures.” In thismanner, the coding engine (632) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (633) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (630). Operations of the coding engine (632) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 6 ), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (633) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (634). In this manner, the video encoder(603) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (635) may perform prediction searches for the codingengine (632). That is, for a new picture to be coded, the predictor(635) may search the reference picture memory (634) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(635) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (635), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (634).

The controller (650) may manage coding operations of the source coder(630), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (645). The entropy coder (645)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (640) may buffer the coded video sequence(s) as createdby the entropy coder (645) to prepare for transmission via acommunication channel (660), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(640) may merge coded video data from the video coder (603) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (650) may manage operation of the video encoder (603).During coding, the controller (650) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (603) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (603) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (640) may transmit additional datawith the encoded video. The source coder (630) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 7 shows a diagram of a video encoder (703) according to anotherembodiment of the disclosure. The video encoder (703) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (703) is used in theplace of the video encoder (403) in the FIG. 4 example.

In an HEVC example, the video encoder (703) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (703) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (703) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(703) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (703) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 7 example, the video encoder (703) includes the interencoder (730), an intra encoder (722), a residue calculator (723), aswitch (726), a residue encoder (724), a general controller (721), andan entropy encoder (725) coupled together as shown in FIG. 7 .

The inter encoder (730) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (722) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (722) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (721) is configured to determine general controldata and control other components of the video encoder (703) based onthe general control data. In an example, the general controller (721)determines the mode of the block, and provides a control signal to theswitch (726) based on the mode. For example, when the mode is the intramode, the general controller (721) controls the switch (726) to selectthe intra mode result for use by the residue calculator (723), andcontrols the entropy encoder (725) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(721) controls the switch (726) to select the inter prediction resultfor use by the residue calculator (723), and controls the entropyencoder (725) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (723) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (722) or the inter encoder (730). Theresidue encoder (724) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (724) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (703) also includes a residuedecoder (728). The residue decoder (728) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (722) and theinter encoder (730). For example, the inter encoder (730) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (722) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (725) is configured to format the bitstream toinclude the encoded block. The entropy encoder (725) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (725) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 8 shows a diagram of a video decoder (810) according to anotherembodiment of the disclosure. The video decoder (810) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (810) is used in the place of the videodecoder (410) in the FIG. 4 example.

In the FIG. 8 example, the video decoder (810) includes an entropydecoder (871), an inter decoder (880), a residue decoder (873), areconstruction module (874), and an intra decoder (872) coupled togetheras shown in FIG. 8 .

The entropy decoder (871) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (872) or the inter decoder (880), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (880); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (872). The residual information can be subject to inversequantization and is provided to the residue decoder (873).

The inter decoder (880) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (872) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (873) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (873) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (871) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (874) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (873) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (403), (603), and (703), and thevideo decoders (410), (510), and (810) can be implemented using anysuitable technique. In an embodiment, the video encoders (403), (603),and (703), and the video decoders (410), (510), and (810) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (403), (603), and (603), and the videodecoders (410), (510), and (810) can be implemented using one or moreprocessors that execute software instructions.

The disclosure includes improvements on most probable mode (MPM) listconstruction.

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published theH.265/HEVC (High Efficiency Video Coding) standard in 2013 (version 1),2014 (version 2), 2015 (version 3), and 2016 (version 4). In 2015, thesetwo standard organizations jointly formed the JVET (Joint VideoExploration Team) to explore the potential of developing the next videocoding standard beyond HEVC. In April 2018, JVET formally launched thestandardization process of next-generation video coding beyond HEVC. Thenew standard was named Versatile Video Coding (VVC), and JVET wasrenamed as Joint Video Expert Team. In July 2020, H.266/VVC version 1was finalized. In January 2021, an ad hoc group was established toinvestigate enhanced compression beyond VVC capability.

To form a MPM list, in one example, a general MPM list with 22 entriescan be constructed first. The first 6 entries in the general MPM listcan be included into a Primary MPM (PMPM) list, and the rest of entriescan form a Secondary MPM (SMPM) list. A first entry in the general MPMlist can be a Planar mode. The remaining entries in the general MPM listcan include (i) the intra modes of the left (L), above (A), below-left(BL), above-right (AR), and above-left (AL) neighbouring blocks, (ii)directional modes with added offset from the first two availabledirectional modes of neighbouring blocks, and (iii) default modes. Thepositions of the L, A, BL, AR, and AL neighboring blocks can be shown inFIG. 9 .

If a height of a CU block (e.g., (902) in FIG. 9 ) is not smaller than awidth of the CU block, the order of neighbouring blocks can be A, L, BL,AR, and AL; otherwise, the order of the neighboring blocks can be L, A,BL, AR, and AL. The order of MPM entry can be important because theindex of entry can be coded with truncated binary. The latter of thetruncated binary can cost more bits to code.

When the neighbouring blocks AL, A, and AR are in a coding tree unit(CTU) different from a CTU of the current CU (e.g., (902)), theneighbouring blocks AL, A, and AR can be considered unavailable due tothe limitation of a line buffer. Accordingly, intra modes of unavailableneighbor CUs may not be inserted into the MPM list.

A propagated intra mode can also be applied for the MPM listconstruction. For example, in VVC, when a neighbor CU is an inter codedCU, an intra mode of that neighbor CU can be considered as a Planar modeand is inserted into the MPM list.

An intra mode of an intra coded CU can be stored in a memory in a unitof 4×4 pixel samples. For an intra coded CU where a decode side intramode derivation (DIMD) is applied, a decoder side derived intra modebased on DIMD with a highest histogram of gradient (HoG) can be storedin the memory. For an intra coded CU where a template-based intra modederivation (TIMD) is applied, a decoder side derived intra mode with asmallest sum of absolute transformed difference (SATD) cost can bestored. For an intra coded CU where a block-based delta pulse codemodulation (BDPCM) is applied, a signaled BDPCM direction can be stored.For an intra coded CU where matrix-based intra prediction (MIP) ortemplate matching prediction (TMP) is applied, the Planar mode can bestored. For other intra coded CUs, intra modes derived from a MPM listor a non-MPM list can be stored.

To improve the accuracy of the MPM list, when a neighbouring block isinter coded, a propagated intra prediction mode can be derived using themotion vector and reference picture. For an inter coded CU, an intramode can be propagated from a referenced area to the inter coded CU.

Intra template matching prediction (also referred to as Intra TMP) is aspecial intra prediction mode that copies a best prediction block fromthe reconstructed part of the current frame, whose L-shaped templatematches the current template (e.g., a template of a current block). Fora predefined search range, the encoder searches for the most similartemplate to the current template in a reconstructed part of the currentframe and uses the corresponding block as a prediction block, where themost similar template is associated with the corresponding block and thecurrent template is associated with the current block. The encoder thensignals the usage of the intra TMP mode, and the same predictionoperation can be performed at the decoder side. A matching block (orcorresponding block) (1002) can be illustrated in FIG. 10 and act as thematching area for the current CU (1004).

As shown in FIG. 10 , the prediction signal can be generated by matchingthe L-shaped causal neighbors (or L-shaped template) of the currentblock (1004) with another block in a predefined search area. Anexemplary predefined search area can include R1 (a current CTU), R2 (atop-left CTU), R3 (an above CTU), and R4 (a left CTU). A sum of absolutedifferences (SAD) can be used as a cost function.

Within each search area, the decoder can search for a template of ablock that has a least SAD with respect to the current template (e.g.,the template of the current block (1004)) and use the block with theleast SAD as a corresponding block of the current block. Thecorresponding block can further act as a prediction block for thecurrent block (e.g., (1004)).

The dimensions of all search regions (e.g., SearchRange_w,SearchRange_h) can be set proportional to the block dimension (e.g.,BlkW, BlkH) of the current block. Accordingly, a fixed number of SADcomparisons can be obtained in each pixel. For example, the dimensionsof a search region (or search range) can be defined in Equations 1 and 2as follows:

SearchRange_w=a*BlkW  Eq. (1)

SearchRange_h=a*BlkH  Eq. (2)

where “a” is a constant that controls a trade-off between a gain and acomplexity of the search process. In an example, “a” is equal to 5.

The Intra TMP can be enabled for CUs of certain sized. For example, theIntra TMP can be enabled for CUs with a size less than or equal to 64 ina width and a height. A maximum CU size for Intra TMP can beconfigurable. The Intra TMP mode can be signaled. For example, the IntraTMP mode can be signaled at a CU level through a dedicated flag.

In a derived mode (DM) for chroma, a chroma CU can have a collocatedluma CU. An intra mode of the collocated luma CU of the chroma CU can beused as an intra mode of the chroma CU.

When a position (x, y) specifies a top-left sample of a chroma CUrelative to the current picture and the chroma CU includes a width of Wand a height of H, a location of the collocated luma CU of the chroma CUcan be (x+W/2, y+H/2). When the collocated luma CU is not intra coded, adefault value (e.g., DC or planar) can be used as the intra mode of thecollocated luma CU.

If the collocated luma CU is one of certain modes such as intra blockcopy (IBC) or palette coding (PLT) coded, the intra mode of thecollocated luma CU can be considered as a DC mode. Otherwise, the intramode of the collocated luma CU can be an intra mode of a CU whichcontains the location (x+W/2, y+H/2).

FIG. 11 shows an exemplary derived mode for chroma that includes achroma CU (1104) and a luma area (1102) associated with the chroma CU(1104). As shown in FIG. 11 , the chroma CU (1104) can include acorresponding position (1106). The corresponding position (1106) caninclude a first coordinate value on a first axis (e.g., X axis) and asecond coordinate value on a second axis (e.g., Y axis) that arerelative to a reference point on the chroma CU (1104). For example, thereference point can be a lower left corner of the chroma CU (1104). Thefirst axis can be perpendicular to the second axis. In some embodiments,the corresponding position (1106) can have a location of (W/2, H/2) withrespect to the lower left corner of the chroma CU (1104), where the W isa width of the chroma CU (1104) and the H is a height of the chroma CU(1104). Thus, the corresponding position (1106) can be a center of thechroma CU (1104). FIG. 11 is merely an example, and the correspondingposition (1106) can be located at any position of the chroma CU (1104)and the reference point can also be located at any position of thechroma CU (1104). A collocated luma CU of the chroma CU (1104) can be aluma CU (1108) that includes the corresponding position (1106) in theluma area (1102).

A universal intra mode map can be used to store intra modes in the unitof samples. Any intra modes can be stored including a signaled, adecoder derived, a default, or a propagated intra mode. The unit ofsamples can be implicitly predefined or explicitly signaled. Forexample, an encoder and a decoder can implicitly predefine a 4×4 pixelas a unit, or explicitly signal 2×2 or 8×8 in the bitstream. Note that,the universal intra mode map can span across CUs or CTUs. Further, notonly an intra or an inter CU can store an intra mode, but also all theCUs can store intra modes.

An example of a partial universal intra mode map is illustrated in FIGS.12A and 12B, where each square can represent a 4×4 unit of samples.

In an embodiment, the universal intra mode map can be empty in thebeginning. Further, the universal intra mode map can store or otherwiseinclude a signaled, a decoder derived, and/or a propagated intra modethat is obtained during a decoding process.

In another embodiment, a default intra mode can be used to initializethe universal intra mode map in the beginning. Further, the defaultintra mode can be replaced by a signaled, a decoder derived, or apropagated intra mode that is obtained during the decoding process. Forexample, as shown in FIG. 12A, a default intra mode 0 (or Planar) can bestored in all the units of a universal intra mode map (1202). Later, thedefault intra mode 0 can be replaced by another intra mode. For example,the other intra mode can be a signaled intra mode, a decoder derivedintra mode, or a propagated intra mode.

In yet another embodiment, the universal intra mode map can be empty inthe beginning. Further, some of the empty (or blank) units of theuniversal intra mode map can store the signaled, decoder derived, and/orpropagated intra modes that are achieved during a decoding process.After a CU is decoded, the remaining blank units can be filled with adefault intra mode, such as the intra mode 0 (or Planar).

As shown in FIG. 12B, a universal intra mode map (1204) can be empty atfirst, and some of the empty units can be filled with intra modes duringa decoding process. After the CU is decoded, blank units (e.g., (1206)and (1208)) can be filled with a default intra mode, such as an intramode 0 (or Planar).

The propagated intra mode can make a non-intra coded CU include apropagated intra mode, which can diversify the possible intra modes thata non-intra coded CU can have. In the disclosure, an improvement on theintra mode propagation is provided, including improvements to thepropagation for the TMP mode and the derived mode of chroma.

In an embodiment, an intra mode of a matching area can be propagated toa current block for TMP mode. The matching area of the current block (orcurrent CU) can be a matched predictor found in a search region using anL-shaped template. A template with other shapes can also be applied. Thesearch regions can be a reconstructed region. The search region and thecurrent block can be included in a same frame or a same picture. In someembodiments, an L-shaped template of the matching area and an L-shapedtemplate of the current block can have a minimum cost value (e.g., SAD)in the search region. The L-shaped template of the matching area caninclude neighboring pixels, such as adjacent to a left side and a topside of the matching area. The L-shaped template of the current CU caninclude neighboring pixels, such as adjacent to a left side and a topside of the current CU.

A corresponding position (e.g., correspondPosition (a, b)) of thecurrent CU can be used to derive the propagated intra mode. Thecorresponding position can be any position inside the current CU. Forexample, the corresponding position can be located at a center of thecurrent CU. The corresponding position can include a first coordinatevalue (e.g., a) on a first axis (e.g., X axis) and a second coordinatevalue (e.g., b) on a second axis (e.g., Y axis) that are relative to areference point, such as a lower left corner of the current block, wherethe first axis can be perpendicular to the second axis.

The corresponding position can be predefined and implicitly agreed onboth an encoder and a decoder. Alternatively, the corresponding positioncan be signaled, explicitly or implicitly, in a bitstream in band or outof band.

In an example, a CU that contains the corresponding position (e.g.,correspondPosition (a, b)) inside the matching area can be acorresponding CU of the current block, regardless of how thecorresponding CU is coded. Thus, the corresponding position inside thematching area can include the first coordinate value (e.g., a) on thefirst axis (e.g., X axis) and the second coordinate value (e.g., b) onthe second axis (e.g., Y axis) that are relative to a reference point,such as a lower left corner of the matching area.

In the disclosure, any kind or combination of intra modes (e.g., anormal intra mode, a propagated intra mode, a default intra mode, andthe like) of the corresponding CU can be propagated to the current CUbased on the TMP mode. The intra mode that is propagated to the currentblock can further be stored and propagate to upcoming CUs.

FIG. 13 shows an exemplary corresponding CU (1308) of a current block(1304). As shown in FIG. 13 , the corresponding CU (1308) can beincluded in a matching area (1306). The matching area (1306) can be areconstructed area in a picture (1302). The current block 1304 can alsobe included in the picture (1302). The matching area (1306) can have atemplate, such as an L-shaped template (1316). As shown in FIG. 13 , theL-shaped template (1316) can include areas that are adjacent to a leftside and a top side of the matching area. The current CU (1304) can havea template, such as an L-shaped template (1318). The L-shaped template(1318) can include areas that are adjacent to a left side and a top sideof the current CU. The L-shaped template of the matching area and theL-shaped template of the current block can have a minimum cost value(e.g., SAD) in a search region in the picture (1302). FIG. 13 is merelyan example. The template (1316) and the template (1318) can includeregions with other shapes that are adjacent to the matching area (1306)and the current CU (1304), respectively.

In an example, the current CU (1304) can have a corresponding position(1312) in any location of the current CU (1304) and have a location of(a, b), where a is a first coordinate value on a first axis (e.g., X)and b is a second coordinate value on a second axis (e.g., Y) relativeto a reference point on the current CU (1304). The reference point canbe located at any position of the current CU (1304). For example, thereference point can be a lower left corner (1314) of the current CU(1304). The corresponding position can be located at any position of thecurrent CU (1304). For example, the corresponding position (1312) of thecurrent CU (1304) can be located at a center of the current CU (1304).Accordingly, the corresponding position (1312) can have a location of(W/2, H/2) relative to the lower left corner of the current CU (1304),where W and H are a width and a height of current CU (1304),respectively. A CU (e.g., (1308)) that contains a corresponding position(1310) in the matching area (1306) can be denoted as the correspondingCU (1308) of the current CU (1304). The corresponding position (1310) ofthe matching area (1306) can also have the location (a, b) on the firstand second axes with respect to a reference point (e.g., a lower leftcorner (1320)) on the matching area (1306). Thus, when the correspondingposition (1312) has a location of (W/2, H/2) with respect to the leftcorner of the current CU (1304), the corresponding position (1310) canhave the location of (W/2, H/2) with respect to a lower left corner ofthe matching area (1306).

In another example, when the corresponding position (1312) has alocation of (W/2, H/2) with respect to a reference point on the currentCU (1304), such as the left corner (1314) of the current CU (1304), thecorresponding position (1310) can have a location of (W′/2, H′/2) withrespect to a reference point on the matching area (1306), such as thelower left corner (1320) of the matching area (1306), where W′ and H′are a width and a height of the matching area (1306), respectively.

In yet another example, the corresponding position (1312) can have alocation of (W/a, H/b) with respect to the reference point, such as theleft corner (1314) of the current CU (1304), and the correspondingposition (1310) can have a location of (W′/a, H′/b) with respect to thereference point on the matching area (1306), such as the lower leftcorner (1320) of the matching area (1306), where a and b are positiveintegers. In some embodiments, W is not equal to W′ and H is not equalto H′. In some embodiments, W can be equal to W′, and H can be equal toH′. Thus, a size of the matching area (1306) is equal to a size of thecurrent CU (1304).

The intra mode of the corresponding CU (1308) can be used as an intramode of the current CU (1304) based on the TMP mode. The intra mode canfurther be stored with the unit of 4×4 pixel samples and propagated toupcoming CUs.

In another embodiment, an intra mode of a current CU can be achieved byaccessing the corresponding position's entry (or assigned intra mode) ina universal intra mode map. The intra mode that is achieved through theuniversal intra mode map can further be stored and propagated toupcoming CUs.

For example, as shown in FIG. 14 , a picture (1402) can include acurrent CU (1404) and a matching area (1406) of the current block(1404). The current CU (1404) can include a corresponding position(1414) and a corresponding CU (1408) inside the matching area (1406).The corresponding CU (1408) can include a corresponding position (1412).The corresponding position (1414) can be located at any location of thecurrent CU (1404). The corresponding position (1414) can have a locationof (a, b), where a is a first coordinate value on a first axis (e.g., X)and b is a second coordinate value on a second axis (e.g., Y) relativeto a reference point on the current CU (1404). The reference point onthe current CU (1404) can be located at any location of the current CU(1404), such as a lower left corner (1461) of the current CU (1404).

In an example, the corresponding position (1414) can be located at acenter of the current CU (1404). Thus, the corresponding position (1414)can have a location of (W/2, H/2), where W and H are a width and aheight of current CU (1404), respectively. The corresponding position(1412) can also have the location of (a, b) with respect to a referencepoint on the matching area (1406). The reference point on the matchingarea (1406) can be located at any location of the matching area (1406),such as a lower left corner (1418) of the matching area (1406).Accordingly, when the corresponding position (1414) has a location of(W/2, H/2) with respect to the lower left corner (1416) of the currentCU (1404), the corresponding position (1412) can have the location of(W/2, H/2) with respect to a lower left corner (1418) of the matchingarea (1406).

In another example, the corresponding position (1414) can have alocation of (W/a, H/b) with respect to the left corner (1416) of thecurrent CU (1404), and the corresponding position (1412) can have alocation of (W′/a, H′/b) with respect to the lower left corner (1418) ofthe matching area (1406). W and H are a width and a height of thecurrent CU (1404), respectively. W′ and H′ are a width and a height ofthe matching area (1406), respectively. In some embodiments, W is notequal to W′ and H is not equal to H′. In some embodiments, W can beequal to W′, and H can be equal to H′.

Further, a universal map (1410) can be assigned to the matching area(1406). The universal map (1410) can divide the matching area (1406)into a plurality of sub areas. Each of the plurality of sub areas can beassigned with a specific intra mode. Thus, the intra mode (e.g., intramode (51)) assigned to the sub area that contains the correspondingposition (1412) can be propagated to the current CU (1404).

In the disclosure, a current chroma CU can have a collocated luma CU.The collocated luma CU can be associated with the current chroma CU. Forexample, both the collocated luma CU and the luma CU can have acorresponding position (e.g., correspondPositionDM (a, b)) and beincluded in a coding tree unit (CTU). In some embodiments, the currentchroma CU can be aligned with the collocated luma CU. According to thechroma DM mode, an intra mode of the collocated luma CU of the currentchroma CU can be propagated to the current chroma CU. When the chroma DMmode is used, the collocated luma CU can be coded with an intraprediction mode as well as other prediction modes, such as intra blockcopy (IBC), an inter mode, PLT, and the like. Thus, the correspondingposition (e.g., correspondPositionDM (a, b)) can be applied to derivethe propagated intra mode from the collocated luma CU to the currentchroma CU.

The corresponding position can be predefined and implicitly agreed onboth an encoder and a decoder. Alternatively, the collocated position(or corresponding position) can be explicitly or implicitly signaled ina bitstream in band or out of band. Further, the corresponding positioncan be located at any location of the chroma CU and include a location(a, b), where a is a first coordinate value on a first axis (e.g., X)and b is a second coordinate value on a second axis (e.g., Y) relativeto a reference point of the current chroma CU, such as a lower leftcorner of the current chroma CU.

In an embodiment, according to the chroma DM mode, any kind of intramodes that are associated with the collocated luma CU, such as a normalintra mode, a propagated intra mode, a default intra mode, or the like,can be propagated to the current chroma CU.

Further, when the collocated luma CU is coded in certain modes such asIBC or inter coded, instead of using a default intra mode value of thecollocated luma CU, a propagated intra mode of the collocated luma CUcan be propagated to the current chroma CU. The propagated intra mode ofthe collocated luma CU can be obtained based on intra modes ofneighboring luma CUs of the collocated luma CU. In such a case, thecurrent chroma CU can have values other than the default intra modevalue from the IBC or inter coded collocated luma CU.

In another embodiment, an intra mode of a current chroma CU can beachieved by accessing an entry (or an intra mode) of a universal intramode map that is assigned to the collocated luma CU according to aposition of the collocated luma CU in the universal intra mode map. Theuniversal intra mode map can divide the collocated luma CU into aplurality of sub areas. Each of the plurality of sub areas can beassigned to a respective intra mode according to the universal intramode map. The intra mode assigned to the sub area that contains thecorresponding position can be propagated to the current chroma CU.

FIG. 15 shows a flow chart outlining a first exemplary decoding process(1500) according to some embodiments of the disclosure. FIG. 16 shows aflow chart outlining a second exemplary decoding process (1600)according to some embodiments of the disclosure. FIG. 17 shows a flowchart outlining a first exemplary encoding process (1700) according tosome embodiments of the disclosure. FIG. 18 shows a flow chart outlininga second exemplary encoding process (1800) according to some embodimentsof the disclosure. The proposed processes may be used separately orcombined in any order. Further, each of the processes (or embodiments),encoder, and decoder may be implemented by processing circuitry (e.g.,one or more processors or one or more integrated circuits). In oneexample, the one or more processors execute a program that is stored ina non-transitory computer-readable medium.

In embodiments, any operations of processes (e.g., (1500), (1600),(1700), and (1800)) may be combined or arranged in any amount or order,as desired. In embodiments, two or more of the operations of theprocesses (e.g., (1500), (1600), (1700), and (1800)) may be performed inparallel.

The processes (e.g., (1500), (1600), (1700), and (1800)) can be used inthe reconstruction and/or encoding of a block, so as to generate aprediction block for the block under reconstruction. In variousembodiments, the processes (e.g., (1500), (1600), (1700), and (1800))are executed by processing circuitry, such as the processing circuitryin the terminal devices (210), (220), (230) and (240), the processingcircuitry that performs functions of the video encoder (303), theprocessing circuitry that performs functions of the video decoder (310),the processing circuitry that performs functions of the video decoder(410), the processing circuitry that performs functions of the videoencoder (503), and the like. In some embodiments, the processes (e.g.,(1500), (1600), (1700), and (1800)) are implemented in softwareinstructions, thus when the processing circuitry executes the softwareinstructions, the processing circuitry performs the processes (e.g.,(1500), (1600), (1700), and (1800)).

As shown in FIG. 15 , the process (1500) can start from (S1501) andproceed to (S1510). At (S1510), coded information of (i) a current blockof a picture and (ii) a reconstructed area of the picture can bereceived from a coded video bitstream.

At (S1520), a matching area of the current block in the reconstructedarea of the picture can be determined.

At (S1530), a first corresponding position of the current block can bedetermined inside the current block. The first corresponding positioncan include a first coordinate value on a first axis and a secondcoordinate value on a second axis relative to a first reference point onthe current block. The first axis can be perpendicular to the secondaxis.

At (S1540), a corresponding block of the current block can be determinedin the matching area. The corresponding block can include a secondcorresponding position that has the first coordinate value on the firstaxis and the second coordinate value on the second axis relative to asecond reference point on the matching area.

At (S1550), an intra prediction mode of the current block can bedetermined based on the corresponding block.

To determine the matching area, a plurality of candidate matching areascan be searched in the reconstructed area of the picture. A respectivecost value between a template region of the current block and arespective template region of each of the plurality candidate matchingareas can be determined. The matching area can be determined as acandidate matching area with a minimum cost value from the plurality ofcandidate matching areas. The template region of the current block caninclude a first region adjacent to a left side of the current block anda second region adjacent to a top side of the current block. Therespective template region of each of the plurality of candidatematching areas can include a first region adjacent to a left side of therespective one of the plurality of candidate matching areas and a secondregion adjacent to a top side of the respective one of the plurality ofcandidate matching areas.

In some embodiments, the first corresponding position of the currentblock can be predefined or signaled in the coded information.

In some embodiments, the first corresponding position can be the centerof the current block.

In some embodiments, an intra prediction mode of the corresponding blockcan be determined as the intra prediction mode of the current block.

In some embodiments, the intra prediction mode of the current block canbe determined based on a universal intra mode map. The universal intramode map can divide the matching area into a plurality of sub areas.Each of the plurality of sub areas can be associated with a respectiveintra prediction mode. The intra prediction mode of the current blockcan be the intra prediction mode associated with a sub area of theplurality of sub areas that includes the second corresponding position.

As shown in FIG. 16 , the process (1600) can start from (S1601) andproceed to (S1610). At (S1610), coded information of (i) a chroma codingunit (CU) and (ii) a luma area can be received from a coded videobitstream.

At (S1620), a corresponding position of the chroma CU can be determinedinside the chroma CU. The corresponding position can include a firstcoordinate value on a first axis and a second coordinate value on asecond axis. The first axis can be perpendicular to the second axis.

At (S1630), a collocated luma CU of the chroma CU can be determined inthe luma area. The collocated luma CU can include the correspondingposition.

At (S1640), an intra prediction mode of the chroma CU can be determinedbased on the collocated luma CU.

In an embodiment, in response to the collocated luma CU being intracoded based on an intra prediction mode, the intra prediction mode ofthe collocated luma CU can be determined as the intra prediction mode ofthe chroma CU. In other embodiments, in response to the collocated lumaCU not being intra coded, a propagated intra mode of the collocated lumaCU can be determined as the intra prediction mode of the chroma CU. Thepropagated intra mode of the collocated luma CU can be obtained based onintra prediction modes of neighboring luma CUs of the collocated lumaCU.

In some embodiments, the corresponding position of the chroma CU can bepredefined or signaled in the coded information.

In some embodiments, the intra prediction mode of the chroma CU can bedetermined based on a universal intra mode map. The universal intra modemap can divide the luma area into a plurality of sub areas. Each of theplurality of sub areas can be assigned with a respective intraprediction mode. The intra prediction mode of the chroma CU can be theintra prediction mode associated with a sub area of the plurality of subareas that include the corresponding position.

As shown in FIG. 17 , the process (1700) can start from (S1701) andproceed to (S1710). At (S1710), a matching area of a current block of apicture can be determined from a reconstructed area of the picture.

At (S1720), a first corresponding position of the current block can bedetermined inside the current block. The first corresponding positioncan include a first coordinate value on a first axis and a secondcoordinate value on a second axis relative to a first reference point onthe current block, where the first axis can be perpendicular to thesecond axis.

At (S1730), a corresponding block of the current block can be determinedfrom the matching area, where the corresponding block can include asecond corresponding position that has the first coordinate value on thefirst axis and the second coordinate value on the second axis relativeto a second reference point on the matching area.

At (S1740), an intra prediction mode of the current block can bedetermined based on the corresponding block.

At (S1750), an intra prediction can be performed on the current blockbased on the determined intra prediction mode.

As shown in FIG. 18 , the process (1800) can start from (S1801) andproceed to (S1810). At (S1810), a corresponding position of a chroma CUcan be determined inside the chroma CU. The corresponding position caninclude a first coordinate value on a first axis and a second coordinatevalue on a second axis, where the first axis can be perpendicular to thesecond axis.

At (S1820), a collocated luma CU of the chroma CU can be determined in aluma area, where the collocated luma CU can include the correspondingposition.

At (S1830), an intra prediction mode of the chroma CU can be determinedbased on the collocated luma CU.

At (S1840), an intra prediction can be performed on the chroma CU basedon the determined intra prediction mode.

At (S1850), a coded video bitstream can be generated to include codeinformation of (i) the chroma CU and (ii) the luma area.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 19 shows a computersystem (1900) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 19 for computer system (1900) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1900).

Computer system (1900) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1901), mouse (1902), trackpad (1903), touchscreen (1910), data-glove (not shown), joystick (1905), microphone(1906), scanner (1907), camera (1908).

Computer system (1900) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1910), data-glove (not shown), or joystick (1905), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1909), headphones(not depicted)), visual output devices (such as screens (1910) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability—some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1900) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1920) with CD/DVD or the like media (1921), thumb-drive (1922),removable hard drive or solid state drive (1923), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1900) can also include an interface (1954) to one ormore communication networks (1955). Networks can for example bewireless, wireline, optical. Networks can further be local, wide-area,metropolitan, vehicular and industrial, real-time, delay-tolerant, andso on. Examples of networks include local area networks such asEthernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G,LTE and the like, TV wireline or wireless wide area digital networks toinclude cable TV, satellite TV, and terrestrial broadcast TV, vehicularand industrial to include CANBus, and so forth. Certain networkscommonly require external network interface adapters that attached tocertain general purpose data ports or peripheral buses (1949) (such as,for example USB ports of the computer system (1900)); others arecommonly integrated into the core of the computer system (1900) byattachment to a system bus as described below (for example Ethernetinterface into a PC computer system or cellular network interface into asmartphone computer system). Using any of these networks, computersystem (1900) can communicate with other entities. Such communicationcan be uni-directional, receive only (for example, broadcast TV),uni-directional send-only (for example CANbus to certain CANbusdevices), or bi-directional, for example to other computer systems usinglocal or wide area digital networks. Certain protocols and protocolstacks can be used on each of those networks and network interfaces asdescribed above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1940) of thecomputer system (1900).

The core (1940) can include one or more Central Processing Units (CPU)(1941), Graphics Processing Units (GPU) (1942), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1943), hardware accelerators for certain tasks (1944), graphicsadapters (1950), and so forth. These devices, along with Read-onlymemory (ROM) (1945), Random-access memory (1946), internal mass storagesuch as internal non-user accessible hard drives, SSDs, and the like(1947), may be connected through a system bus (1948). In some computersystems, the system bus (1948) can be accessible in the form of one ormore physical plugs to enable extensions by additional CPUs, GPU, andthe like. The peripheral devices can be attached either directly to thecore's system bus (1948), or through a peripheral bus (1949). In anexample, the screen (1910) can be connected to the graphics adapter(1950). Architectures for a peripheral bus include PCI, USB, and thelike.

CPUs (1941), GPUs (1942), FPGAs (1943), and accelerators (1944) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1945) or RAM (1946). Transitional data can also be stored in RAM(1946), whereas permanent data can be stored for example, in theinternal mass storage (1947). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1941), GPU (1942), massstorage (1947), ROM (1945), RAM (1946), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1900), and specifically the core (1940) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1940) that are of non-transitorynature, such as core-internal mass storage (1947) or ROM (1945). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1940). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1940) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1946) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1944)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

APPENDIX A: ACRONYMS

-   JEM: joint exploration model-   VVC: versatile video coding-   BMS: benchmark set-   MV: Motion Vector-   HEVC: High Efficiency Video Coding-   SEI: Supplementary Enhancement Information-   VUI: Video Usability Information-   GOPs: Groups of Pictures-   TUs: Transform Units,-   PUs: Prediction Units-   CTUs: Coding Tree Units-   CTBs: Coding Tree Blocks-   PBs: Prediction Blocks-   HRD: Hypothetical Reference Decoder-   SNR: Signal Noise Ratio-   CPUs: Central Processing Units-   GPUs: Graphics Processing Units-   CRT: Cathode Ray Tube-   LCD: Liquid-Crystal Display-   OLED: Organic Light-Emitting Diode-   CD: Compact Disc-   DVD: Digital Video Disc-   ROM: Read-Only Memory-   RAM: Random Access Memory-   ASIC: Application-Specific Integrated Circuit-   PLD: Programmable Logic Device-   LAN: Local Area Network-   GSM: Global System for Mobile communications-   LTE: Long-Term Evolution-   CANBus: Controller Area Network Bus-   USB: Universal Serial Bus-   PCI: Peripheral Component Interconnect-   FPGA: Field Programmable Gate Areas-   SSD: solid-state drive-   IC: Integrated Circuit-   CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method of video decoding performed in a videodecoder, the method comprising: receiving coded information of (i) acurrent block of a picture and (ii) a reconstructed area of the picturefrom a coded video bitstream; determining a matching area of the currentblock in the reconstructed area of the picture; determining a firstcorresponding position of the current block inside the current block,the first corresponding position including a first coordinate value on afirst axis and a second coordinate value on a second axis relative to afirst reference point on the current block, the first axis beingperpendicular to the second axis; determining a corresponding block ofthe current block in the matching area, the corresponding blockincluding a second corresponding position that has the first coordinatevalue on the first axis and the second coordinate value on the secondaxis relative to a second reference point on the matching area; anddetermining an intra prediction mode of the current block based on thecorresponding block.
 2. The method of claim 1, wherein the determiningthe matching area further comprises: searching a plurality of candidatematching areas in the reconstructed area of the picture; determining arespective cost value between a template region of the current block anda respective template region of each of the plurality candidate matchingareas; and determining the matching area as a candidate matching areawith a minimum cost value from the plurality of candidate matchingareas, wherein: the template region of the current block includes afirst region adjacent to a left side of the current block and a secondregion adjacent to a top side of the current block, and the respectivetemplate region of each of the plurality of candidate matching areasincludes a first region adjacent to a left side of the respective one ofthe plurality of candidate matching areas and a second region adjacentto a top side of the respective one of the plurality of candidatematching areas.
 3. The method of claim 1, wherein the firstcorresponding position of the current block is predefined or signaled inthe coded information.
 4. The method of claim 1, wherein the firstcorresponding position is the center of the current block.
 5. The methodof claim 1, wherein the determining the intra prediction mode of thecurrent block further comprises: determining an intra prediction mode ofthe corresponding block as the intra prediction mode of the currentblock.
 6. The method of claim 1, wherein the determining the intraprediction mode of the current block further comprises: determining theintra prediction mode of the current block based on a universal intramode map, the universal intra mode map dividing the matching area into aplurality of sub areas and each of the plurality of sub areas beingassociated with a respective intra prediction mode, the intra predictionmode of the current block being the intra prediction mode associatedwith a sub area of the plurality of sub areas that includes the secondcorresponding position.
 7. A method of video decoding performed in avideo decoder, the method comprising: receiving coded information of (i)a chroma coding unit (CU) and (ii) a luma area from a coded videobitstream; determining a corresponding position of the chroma CU insidethe chroma CU, the corresponding position including a first coordinatevalue on a first axis and a second coordinate value on a second axis,the first axis being perpendicular to the second axis; determining acollocated luma CU of the chroma CU in the luma area, the collocatedluma CU including the corresponding position; and determining an intraprediction mode of the chroma CU based on the collocated luma CU.
 8. Themethod of claim 7, wherein the determining the intra prediction mode ofthe chroma CU further comprises: in response to the collocated luma CUbeing intra coded based on an intra prediction mode, determining theintra prediction mode of the collocated luma CU as the intra predictionmode of the chroma CU; and in response to the collocated luma CU notbeing intra coded, determining a propagated intra mode of the collocatedluma CU as the intra prediction mode of the chroma CU, the propagatedintra mode of the collocated luma CU being obtained based on intraprediction modes of neighboring luma CUs of the collocated luma CU. 9.The method of claim 7, wherein the corresponding position of the chromaCU is predefined or signaled in the coded information.
 10. The method ofclaim 7, wherein the determining the intra prediction mode of the chromaCU further comprises: determining the intra prediction mode of thechroma CU based on a universal intra mode map, the universal intra modemap dividing the luma area into a plurality of sub areas and each of theplurality of sub areas being assigned with a respective intra predictionmode, the intra prediction mode of the chroma CU being the intraprediction mode associated with a sub area of the plurality of sub areasthat include the corresponding position.
 11. An apparatus, comprising:processing circuitry configured to: receive coded information of (i) acurrent block of a picture and (ii) a reconstructed area of the picturefrom a coded video bitstream; determine a matching area of the currentblock in the reconstructed area of the picture; determine a firstcorresponding position of the current block inside the current block,the first corresponding position including a first coordinate value on afirst axis and a second coordinate value on a second axis relative to afirst reference point on the current block, the first axis beingperpendicular to the second axis; determine a corresponding block of thecurrent block in the matching area, the corresponding block including asecond corresponding position that has the first coordinate value on thefirst axis and the second coordinate value on the second axis relativeto a second reference point on the matching area; and determine an intraprediction mode of the current block based on the corresponding block.12. The apparatus of claim 11, wherein the processing circuitry isconfigured to: search a plurality of candidate matching areas in thereconstructed area of the picture; determine a respective cost valuebetween a template region of the current block and a respective templateregion of each of the plurality candidate matching areas; and determinethe matching area as a candidate matching area with a minimum cost valuefrom the plurality of candidate matching areas, wherein: the templateregion of the current block includes a first region adjacent to a leftside of the current block and a second region adjacent to a top side ofthe current block, and the respective template region of each of theplurality of candidate matching areas includes a first region adjacentto a left side of the respective one of the plurality of candidatematching areas and a second region adjacent to a top side of therespective one of the plurality of candidate matching areas.
 13. Theapparatus of claim 11, wherein the first corresponding position of thecurrent block is predefined or signaled in the coded information. 14.The apparatus of claim 11, wherein the first corresponding position isthe center of the current block.
 15. The apparatus of claim 11, whereinprocessing circuitry is configured to: determine an intra predictionmode of the corresponding block as the intra prediction mode of thecurrent block.
 16. The apparatus of claim 11, wherein the processingcircuitry is configured to: determine the intra prediction mode of thecurrent block based on a universal intra mode map, the universal intramode map dividing the matching area into a plurality of sub areas andeach of the plurality of sub areas being associated with a respectiveintra prediction mode, the intra prediction mode of the current blockbeing the intra prediction mode associated with a sub area of theplurality of sub areas that includes the second corresponding position.17. An apparatus, comprising: processing circuitry configured to:receive coded information of (i) a chroma coding unit (CU) and (ii) aluma area from a coded video bitstream; determine a correspondingposition of the chroma CU inside the chroma CU, the correspondingposition including a first coordinate value on a first axis and a secondcoordinate value on a second axis, the first axis being perpendicular tothe second axis; determine a collocated luma CU of the chroma CU in theluma area, the collocated luma CU including the corresponding position;and determine an intra prediction mode of the chroma CU based on thecollocated luma CU.
 18. The apparatus of claim 17, wherein theprocessing circuitry is configured to: in response to the collocatedluma CU being intra coded based on an intra prediction mode, determinethe intra prediction mode of the collocated luma CU as the intraprediction mode of the chroma CU; and in response to the collocated lumaCU not being intra coded, determine a propagated intra mode of thecollocated luma CU as the intra prediction mode of the chroma CU, thepropagated intra mode of the collocated luma CU being obtained based onintra prediction modes of neighboring luma CUs of the collocated lumaCU.
 19. The apparatus of claim 17, wherein the corresponding position ofthe chroma CU is predefined or signaled in the coded information. 20.The apparatus of claim 17, wherein the processing circuitry isconfigured to: determine the intra prediction mode of the chroma CUbased on a universal intra mode map, the universal intra mode mapdividing the luma area into a plurality of sub areas and each of theplurality of sub areas being assigned with a respective intra predictionmode, the intra prediction mode of the chroma CU being the intraprediction mode associated with a sub area of the plurality of sub areasthat include the corresponding position.